Given a 2D array, print it in reverse spiral form. We have already discussed Print a given matrix in spiral form. This article discusses how to do the reverse printing. See the following examples.
Input:
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
Output:
10 11 7 6 5 9 13 14 15 16 12 8 4 3 2 1
Input:
1 2 3 4 5 6
7 8 9 10 11 12
13 14 15 16 17 18
Output:
11 10 9 8 7 13 14 15 16 17 18 12 6 5 4 3 2 1
C++
// This is a modified code of #include <iostream> #define R 3 #define C 6 using namespace std; // Function that print matrix in reverse spiral form. void ReversespiralPrint(int m, int n, int a[R][C]) { // Large array to initialize it // with elements of matrix long int b[100]; /* k - starting row index l - starting column index*/ int i, k = 0, l = 0; // Counter for single dimension array //in which elements will be stored int z = 0; // Total elements in matrix int size = m*n; while (k < m && l < n) { // Variable to store value of matrix. int val; /* Print the first row from the remaining rows */ for (i = l; i < n; ++i) { // printf("%d ", a[k][i]); val = a[k][i]; b[z] = val; ++z; } k++; /* Print the last column from the remaining columns */ for (i = k; i < m; ++i) { // printf("%d ", a[i][n-1]); val = a[i][n-1]; b[z] = val; ++z; } n--; /* Print the last row from the remaining rows */ if ( k < m) { for (i = n-1; i >= l; --i) { // printf("%d ", a[m-1][i]); val = a[m-1][i]; b[z] = val; ++z; } m--; } /* Print the first column from the remaining columns */ if (l < n) { for (i = m-1; i >= k; --i) { // printf("%d ", a[i][l]); val = a[i][l]; b[z] = val; ++z; } l++; } } for (int i=size-1 ; i>=0 ; --i) { cout<<b[i]<<" "; } } /* Driver program to test above functions */int main() { int a[R][C] = { {1, 2, 3, 4, 5, 6}, {7, 8, 9, 10, 11, 12}, {13, 14, 15, 16, 17, 18}}; ReversespiralPrint(R, C, a); return 0; } |
Java
// JAVA Code for Print a given matrix in // reverse spiral form class GFG { public static int R = 3, C = 6; // Function that print matrix in reverse spiral form. public static void ReversespiralPrint(int m, int n, int a[][]) { // Large array to initialize it // with elements of matrix long b[] = new long[100]; /* k - starting row index l - starting column index*/ int i, k = 0, l = 0; // Counter for single dimension array //in which elements will be stored int z = 0; // Total elements in matrix int size = m * n; while (k < m && l < n) { // Variable to store value of matrix. int val; /* Print the first row from the remaining rows */ for (i = l; i < n; ++i) { val = a[k][i]; b[z] = val; ++z; } k++; /* Print the last column from the remaining columns */ for (i = k; i < m; ++i) { val = a[i][n-1]; b[z] = val; ++z; } n--; /* Print the last row from the remaining rows */ if ( k < m) { for (i = n-1; i >= l; --i) { val = a[m-1][i]; b[z] = val; ++z; } m--; } /* Print the first column from the remaining columns */ if (l < n) { for (i = m-1; i >= k; --i) { val = a[i][l]; b[z] = val; ++z; } l++; } } for (int x = size-1 ; x>=0 ; --x) { System.out.print(b[x]+" "); } } /* Driver program to test above function */ public static void main(String[] args) { int a[][] = { {1, 2, 3, 4, 5, 6}, {7, 8, 9, 10, 11, 12}, {13, 14, 15, 16, 17, 18}}; ReversespiralPrint(R, C, a); } } // This code is contributed by Arnav Kr. Mandal. |
Python3
# Python3 Code to Print a given
# matrix in reverse spiral form
# This is a modified code of
# https:#www.geeksforgeeks.org/print-a-given-matrix-in-spiral-form/
R, C = 3, 6
def ReversespiralPrint(m, n, a):
# Large array to initialize it
# with elements of matrix
b = [0 for i in range(100)]
#/* k – starting row index
#l – starting column index*/
i, k, l = 0, 0, 0
# Counter for single dimension array
# in which elements will be stored
z = 0
# Total elements in matrix
size = m * n
while (k < m and l < n): # Variable to store value of matrix. val = 0 # Print the first row # from the remaining rows for i in range(l, n): # printf("%d ", a[k][i]) val = a[k][i] b[z] = val z += 1 k += 1 # Print the last column # from the remaining columns for i in range(k, m): # printf("%d ", a[i][n-1]) val = a[i][n - 1] b[z] = val z += 1 n -= 1 # Print the last row # from the remaining rows if (k < m): for i in range(n - 1, l - 1, -1): # printf("%d ", a[m-1][i]) val = a[m - 1][i] b[z] = val z += 1 m -= 1 # Print the first column # from the remaining columns if (l < n): for i in range(m - 1, k - 1, -1): # printf("%d ", a[i][l]) val = a[i][l] b[z] = val z += 1 l += 1 for i in range(size - 1, -1, -1): print(b[i], end = " ") # Driver Code a = [[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12], [13, 14, 15, 16, 17, 18]] ReversespiralPrint(R, C, a) # This code is contributed by mohit kumar [tabby title="C#"]
// C# Code for Print a given matrix in // reverse spiral form using System; class GFG { public static int R = 3, C = 6; // Function that print matrix in reverse spiral form. public static void ReversespiralPrint(int m, int n, int [,]a) { // Large array to initialize it // with elements of matrix long []b = new long[100]; /* k - starting row index l - starting column index*/ int i, k = 0, l = 0; // Counter for single dimension array //in which elements will be stored int z = 0; // Total elements in matrix int size = m * n; while (k < m && l < n) { // Variable to store value of matrix. int val; /* Print the first row from the remaining rows */ for (i = l; i < n; ++i) { val = a[k,i]; b[z] = val; ++z; } k++; /* Print the last column from the remaining columns */ for (i = k; i < m; ++i) { val = a[i,n-1]; b[z] = val; ++z; } n--; /* Print the last row from the remaining rows */ if ( k < m) { for (i = n-1; i >= l; --i) { val = a[m-1,i]; b[z] = val; ++z; } m--; } /* Print the first column from the remaining columns */ if (l < n) { for (i = m-1; i >= k; --i) { val = a[i,l]; b[z] = val; ++z; } l++; } } for (int x = size-1 ; x>=0 ; --x) { Console.Write(b[x]+" "); } } /* Driver program to test above function */ public static void Main() { int [ ,]a = { {1, 2, 3, 4, 5, 6}, {7, 8, 9, 10, 11, 12}, {13, 14, 15, 16, 17, 18}}; ReversespiralPrint(R, C, a); } } // This code is contributed by vt_m. |
PHP
<?php // PHP Code for Print a given // matrix in reverse spiral form $R=3; $C=6; // Function that print matrix // in reverse spiral form. function ReversespiralPrint($m, $n, array $a) { // Large array to initialize it // with elements of matrix $b; // k - starting row index // l - starting column index $k = 0; $l = 0; // Counter for single dimension array // in which elements will be stored $z = 0; // Total elements in matrix $size = $m*$n; while ($k < $m && $l < $n) { // Variable to store // value of matrix. $val; // Print the first row from // the remaining rows for ($i = $l; $i < $n; ++$i) { $val = $a[$k][$i]; $b[$z] = $val; ++$z; } $k++; // Print the last column from // the remaining columns for ($i = $k; $i < $m; ++$i) { // printf("%d ", a[i][n-1]); $val = $a[$i][$n-1]; $b[$z] = $val; ++$z; } $n--; // Print the last row from // the remaining rows if ( $k < $m) { for ($i = $n-1; $i >= $l; --$i) { // printf("%d ", a[m-1][i]); $val = $a[$m-1][$i]; $b[$z] = $val; ++$z; } $m--; } // Print the first column // from the remaining columns if ($l < $n) { for ($i = $m - 1; $i >= $k; --$i) { $val = $a[$i][$l]; $b[$z] = $val; ++$z; } $l++; } } for ($i = $size - 1; $i >= 0; --$i) { echo $b[$i]." "; } } // Driver Code $a= array(array(1, 2, 3, 4, 5, 6), array(7, 8, 9, 10, 11, 12), array(13, 14, 15, 16, 17, 18)); ReversespiralPrint($R, $C, $a); // This Code is contributed by mits ?> |
Output:
11 10 9 8 7 13 14 15 16 17 18 12 6 5 4 3 2 1
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